The long-term goal of this project is to develop a new class of biocompatible optical devices for light- based therapy, surgery and diagnosis. A variety of optical techniques, such as photochemical tissue bonding and photodynamic therapy, require efficient delivery of light deep into tissues, but the limited penetration of light in tissue constitutes a serious constraint in clinical use. Fiber-optic devices or catheters have been useful in bringing a light source close to the target tissue in the body. However, delivering the light further into the tissue has remained a challenge. In this project, a new approach based on bio-absorbable and implantable light-delivery devices is proposed. This contrasts with conventional optical fibers made of glass or plastic that are not biocompatible and, thus, must be removed from the body soon after use. Using biocompatible polymers, we will develop thin flexible waveguides and use them in a photochemical tissue bonding (PTB) application. The fabricated biodegradable devices can be inserted between the interfaces of tissue to be bonded and induce photochemical bonding in regions into which light can otherwise not penetrate. The devices will be eventually resorbed thus eliminating the need for removal that would most likely damage the tissue bond. The safety and efficacy of this approach will be evaluated in ex-vivo models of skin wound closure and in-vivo animal studies of biocompatibility. While the initial focus of the project is on light delivering devices for PTB, a variety of other bioabsorbable and implantable optical functional devices are envisioned and can make a far-reaching impact in light-based therapy, surgery, and diagnosis. The project is therefore expected to have high impact and might well herald a new paradigm in photomedicine.